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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Au/Pt Bimetallic Nanowires with Stepped Pt Sites for Enhanced C–C Cleavage in C2+ Alcohol Electro-oxidation Reactions

Efficient C–C bond cleavage and oxidation of alcohols to CO 2 is the key to developing highly efficient alcohol fuel cells for renewable energy applications. In this work, we report the synthesis of core/shell Au/Pt nanowires (NWs) with stepped Pt clusters deposited along the ultrathin (2.3 nm) stepped Au NWs as an active catalyst to effectively oxidize alcohols to CO 2 . The catalytic oxidation reaction is dependent on the Au/Pt ratios, and the Au 1.0 /Pt 0.2 NWs have the largest percentage (~75%) of stepped Au/Pt sites and show the highest activity for ethanol electro-oxidation, reaching an unprecedented 196.9 A/mg Pt (32.5 A/mg Pt+Au ). This NW catalyst is also active in catalyzing the oxidation of other primary alcohols, such as methanol, n-propanol, and ethylene glycol. In situ X-ray absorption spectroscopy and infrared spectroscopy are used to characterize the catalyst structure and to identify key reaction intermediates, providing concrete evidence that the synergy between the low-coordinated Pt sites and the stepped Au NWs is essential to catalyze the alcohol oxidation reaction, which is further supported by DFT calculations that the C–C bond cleavage is indeed enhanced on the undercoordinated Pt–Au surface. Here, our study provides important evidence that a core/shell structure with stepped core/shell sites is essential to enhance electrochemical oxidation of alcohols and will also be central to understanding electro-oxidation reactions and to the future development of highly efficient direct alcohol fuel cells for renewable energy applications.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Shifts in valence states in bimetallic MXenes revealed by electron energy-loss spectroscopy (EELS)

MXenes are an emergent class of two-dimensional materials with a very wide spectrum of promising applications. The synthesis of multiple MXenes, specifically solid-solution MXenes, allows fine tuning of their properties, expands their range of applications, and leads to enhanced performance. The functionality of solid-solution MXenes is closely related to the valence state of their constituents: transition metals, oxygen, carbon, and nitrogen. However, the impact of changes in the oxidation state of elements in MXenes is not well understood. In this work, three interrelated solid-solution MXene systems (Ti$_{2–y}$Nb$_y$CT$_x$, Nb$_{2–y}$V$_y$CT$_x$, and Ti$_{2–y}$V$_y$CT$_x$) were investigated with scanning transmission electron microscopy and electron energy-loss spectroscopy to determine the localized valence states of metals at the nanoscale. The analysis demonstrates changes in the electronic configuration of V upon modification of the overall composition and within individual MXene flakes. These shifts of oxidation state can explain the nonlinear optical and electronic features of solid-solution MXenes. Vanadium appears to be particularly sensitive to modification of the valence state, while titanium maintains the same oxidation state in Ti–Nb and Ti–V MXenes, regardless of stoichiometry. Here, the study also explains Nb's influential role in the previously observed electronic properties in the Nb–V and Nb–Ti systems.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reactivities of Interstitial Hydrides in a Cu 11 Template: En Route to Bimetallic Clusters

In sharp contrast to surface hydrides, reactivities of interstitial hydrides are difficult to explore. When treated with a metal ion (Cu + , Ag + , and Au + ), the stable CuI dihydride template [Cu 11 H 2 {S 2 P(OiPr) 2 } 6 (C≡CPh) 3 ] (H 2 Cu 11 ) generates surprisingly three very different compounds, namely [CuH 2 Cu 11 {S 2 P(OiPr) 2 } 6 (C≡CPh) 3 ] + (1), [AgH 2 Cu 14 {S 2 P(OiPr) 2 } 6 ((C≡CPh) 6 ] + (2), and [AuCu 11 {S 2 P(OiPr) 2 } 6 (C≡CPh) 3 Cl] (3). Compounds 1 and 2 are both MI species and maintain the same number of hydride ligands as their H 2 Cu 11 precursor. Neutron diffraction revealed the first time a trigonal-pyramidal hydride coordination mode in the AgCu 3 environment of 2. 3 has no hydride and exhibits a mixed-valent [AuCu 11 ] 10+ metal core, making it a two-electron superatom.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Effect of bimetallic modification on blast furnace slag and its application in low‐temperature selective catalytic reduction

Abstract Objective In order to control NO x in low‐temperature flue gases emitted from non‐power industries and to reduce the preparation cost of denitration catalysts, this study uses inexpensive blast furnace slag as raw material to prepare denitration catalysts. Methods After cooling, drying and grinding, the blast furnace slag becomes a powder with considerable fineness and meets the requirements of activity index, which is called GGBS (ground granulated blast furnace slag). Using GGBS as denitration catalyst carrier, the active components M (M = Fe, Co, Ni, Cu and Ce) are loaded on Mn‐based GGBS catalyst using an impregnation method. Conclusions The effect of different active components on the denitration performance and sulfur resistance of Mn‐based GGBS catalysts is investigated. The results show that the Mn‐Ce/GGBS catalyst has better denitration performance and sulfur resistance. The Mn‐Ce/GGBS catalyst has a significant denitration performance when load ratio is 2:1. The active component Ce improves the denitration performance of the catalyst, reduces sulfur poisoning and extends the life of the catalyst. The SO 2 in the flue gas increases the acid sites on the catalyst surface and improves catalyst activity. The larger the ratios of Mn 4+ /Mn 3+ , Ce 4+ /Ce 3+ and O α /O β , the stronger the catalyst activity and the better the denitration performance. © 2022 Society of Chemical Industry (SCI).

Zhang, Lei↗
DOE OSTI2022

The Impact of Rolling at Temperature on Conductivity and Texture in Nanolamellar Cu/Nb Bimetallic Composites

We report warm rolling is used to identify whether reductions in dislocation content would provide a significant impact on conductivity in accumulatively roll-bonded Cu-Nb nanolaminates. In addition, the impact of temperature on mechanical properties and interfacial texture is also quantified. Although temperature has a strong effect on dislocation content and mechanical properties, it is shown that length scale and volume fraction are most critical to defining the conductivity of the nanolaminate. Rolling at temperature reduced the flow stress of the material while maintaining the interfacial and layer structure, indicating that warm rolling can increase the ability to process the nanolaminates without reducing conductivity.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Additive manufacturing of bimetallic structures

Abstract Metals of 12Cr2Si and 9Cr1Mo are investigated with femtosecond fiber laser additive manufacturing. A smooth phase transition is found at the interface of the two gradated composition metals, indicating a strong bonding. In contrast, the comparison group of SS316L and SA508 shows an abrupt transition.

Bai, Shuang↗